The present invention relates to methods for forming commercially valuable structural wood beams from wood waste, and to the beams resulting from such methods.
A variety of existing processes are used to form commercially valuable wood products, including dimension lumber such as 2×4s, 2×6s, 4×4s, etc. and other beams. The most common of these methods is simply to saw lumber from round logs of varying diameters. Though this method is both simple and inexpensive, it will typically produce a great deal of milled wood waste. Because commercial dimension lumber is usually of rectangular cross-sectional dimensions, only the central portion of a round log may be used. Thus, as depicted in FIG. 1A, sawing a log 10 into lumber boards 12 will result in milled wood waste comprising slabs 14, edgings 16, and end trimmings 17 (FIG. 2), the latter resulting from sawing the boards to standard lengths. Further, some round wood simply has an insufficient diameter to saw into any commercial dimension lumber or other types of beams.
Another method used to form commercially valuable wood products rotates a round log in a veneer lathe about its longitudinal axis as a large knife peels thin layers of veneer from its circumference. These layers may then be bonded together to form plywood panels or laminated veneer lumber, for instance. Though this method can produce panels and beams much wider than the diameter of most logs, it also produces wood waste called peeler cores, i.e., the cylindrical portion 18 in FIG. 1B remaining after the log has been peeled to the diametric core limit of the veneer lathe. In addition, some portions of the peeled layers may be unusable for plywood or laminated veneer lumber, and thus constitute veneer waste.
Historically, the foregoing large amount of wood waste has been converted to low-end, less valuable wood products such as pulp chips for paper.
Still another method of forming commercially valuable wood products bonds and compresses wood strands or other particles within a press or mold to fabricate structural wood beams. The wood strands or other particles are mixed with an adhesive before being compressed at high pressure. This method may be used to form either a panel that is later sawed into commercially dimensioned composite beams such as 2×4s, 2×6s, 4×4s, etc., or molded composite beams of contoured cross-sections such as I-beams. Unfortunately, this process is expensive in relation to other methods of forming structural beams. Some of this expense derives from the fact that existing methods of forming composite beams require that the strands or other particles used have uniform, very small cross-sectional dimensions to minimize voids in the resulting product, which tend to weaken it. Thus these existing methods require that the strands be sliced or otherwise divided a number of times before being bonded and compressed into the product, which is time-consuming. Another expensive aspect of this process is the large amount of adhesive needed to bond the strands or other particles of small cross-sectional dimensions to one another.
Historically, the foregoing expense has been further aggravated by the fact that the strands or other particles used in this process have been formed from logs that would otherwise be suitable for forming commercial dimension lumber or veneer from traditional milling processes. Though some had thought that wood waste generated from traditional milling processes might also provide an economical source of wood strands, it has proven too difficult to efficiently form usable strands from such wood waste. One major impediment to the use of wood waste in strand fabrication has been the small cross-sectional strand dimensions needed. Not only is it more difficult to control individual wood waste pieces to insure small-dimensional subdivisions of the pieces, but the comparatively small volume of strand produced for each wood waste piece makes strand fabrication a time-consuming task, particularly since each strand must be repeatedly subdivided before it is suitable for use.
For example, Shibusawa, et al., U.S. Pat. No. 5,814,170, suggests that a structural wood product could be fabricated from strands taken from small-diameter logs by first cutting a log into slender boards and repeatedly subdividing those boards into finely split strands of sufficiently small cross-section. This method is slow and expensive, and does not provide a practical method of forming strands from other forms of wood waste, and particularly the more commonly encountered milled wood waste such as edgings, slabs, and end trimmings. In the same vein, Dietz, U.S. Pat. No. 5,934,348 discusses a method of forming wood strands from logs by placing a number of such logs in a bin and feeding them into a rotating blade. Once again, this particular method requires that the strands produced be of small cross-sectional dimensions, necessitating subdivision of the strands, and is not applicable to most types of wood waste.
Dietz also discloses that strands may first be divided from those residual portions of a saw log not within the usable inner region that would ordinarily become milled wood waste during the milling process. In this disclosed process, the boundaries of the usable inner portion of a saw log are first identified. Then the saw log is directed through a parallel array of knives that each slice into the log to a point on the boundary of the usable region. The saw log is then directed through a lathe, producing strands that may then be subdivided to form usable strands. This method, however, necessitates expensive and complex special sawmill equipment, time-consuming multiple subdivisions of the wood waste, and individual strands of small cross-section.
What is desired, therefore, is a cost efficient process for manufacturing structural wood beams from wood waste and a cost-efficient, strong structural wood beam formed from such wood waste.